Transportation of coal by pipeline



Jan. l5, 1963 E. H. RElcHl.

TRANSPORTATION OF COAL BY PIPELINE 2 Sheets-Sheet 2 Filed May 26, 1961HIS ATTORNEY 3,073,552 Patented dan. 15, 1963 3,073,652 TRANSPURTA'HN 0FCOAL BY PIPEMNE Eric H. Reichl, Pittsburgh, Pa., assigner toConsolidation Coal Company, Pittsburgh, Pa., a corporation of Penn-Sylvania Filed May 26, 196i, Ser. No. 112,965 7 Claims. (Cl. 302-66)This invention relates to a method of transporting coal as a coal-waterslurry through a long distance pipeline to a coal conversion unit. Moreparticularly, this invention relates to a method of transporting acoal-Water slurry at one solids concentration through a long distancepipeline to a concentra-ting terminal and thereafter transporting thecoal-water slurry at a different solids concentration through a secondpipeline to a coal conversion terminal.

A recently discovered process for transporting coal as an aqueous slurryhas made it possible now to transport coal over long distances through apipeline. A commercial pipeline has been constructed to transport coalfrom a mine in southern Ohio to a consumer along the shore of Lake Erie,an actual distance of 108 miles. Several million tons of coal have beensuccessfully transported over this distance through this commercialpipeline at a substantial savings in transportation costs.

The process employed to transport the coal as an aqueous slurry throughthis commercial pipeline is set forth in U.S. Patent #2,791,471 entitledTransportation of Coal by Pipeline. The process described in theaforementioned patent has proved both successful and commerciallyfeasible. The hereinafter described invention is directed to animprovement of the process set forth in the above-mentioned patent.

In any coal pipeline installation there are three basic stages: (l) apreparation stage where the coal is prepared and mixed with water toform a coal-water slurry; (2) a long distance transporta-tion stagewherein the coal- Water slurry is transported from a preparationterminal to a coal conversion terminal by pumping the slurry through apipeline; and (3) a conversion stage where the coal in the slurry isconverted by combustion, gasiiication, chemical reformation or the like.

In the past it has been the practice in the conversion stage to removesubstantially all the Water from the slurry and recover relatively drycoal particles. The dried coal particles are then stored and handled ina conventional manner.

The economics of dewatering, storing and handling the dried coalparticles in the conversion terminal in a sense controlled the size ofthe coal particles that were transported through the long distancepipeline. The dewatering, storing and handling characteristics of thedry particles increased in ditiiculty with the increased content ofextremely ne particles in the product. There are many problems presentin separating extremely line particles from a water slurry that are notpresent when relatively coarse particles are separated from a waterslurry. For instance, the filtration characteristics of a slurry havinga substantial portion of extremely iine particles is unfavorableeconomically. The thermal drying of the filter cake and the clarifyingof the liquid iiltrate are also more difficult when extremely lineparticles are present. There are also dust and explosion hazards presentduring the dewatering and drying process. The storage and handling ofthe line coal particles is another diflicult operation. The accuratemetering or feeding of the dry Iine coal particles to conventionalburning apparatus by conventional known mechanical means is ditcult andthe difficulty is further increased by the presence of extremely ne coalparticles.

In view of the problems encountered in the separation of the water fromthe extremely tine coal particles, it was found highly desirable totransport a slurry which contained a minimum amount of extremely tinecoal particles. It was found, however, that some extremely ne particlesin the slurry were required to obtain desirable pumping characteristics.serve with the water as a vehicle for the coarser coal particles andtend to retain the coarser particles in suspension while beingtransported through the pipeline at lower and more economic velocities.With a sufficient amount of extremely fine coal particles, the dynamicstability of the coal-water slurry is improved and the tendency for thecoal particles -to settle is markedly reduced. It is believed that lessenergy is consumed in maintaining the larger sized particles insuspension while the slurry is being transported through the pipeline.The improved dynamic stability of the slurry also permits greaterlatitude in the velocity at which the slurry is transported through thepipeline.

It is the principal object of this invention to obtain the -advantagesof a more dynamically stable slurry in the long distance pipeline byemploying a substantial amount of extremely tine coal particles in theslurry and to further eliminate the hazards and problems encountered inremoving substantially all of the water from the slurry in the coalconversion terminal. By my invention it is now possible to transport adynamically stable slurry over long distances through a pipeline atoptimum pumping costs and to further eliminate a substantial portion ofthe mechanical equipment required to remove the water from the slurry inthe coal conversion terminal. By my irnproved method of transportation,a dynamically stable coal-water slurry having a predetermined sizedistribution of coal particles and solids concentration is transportedthrough a long distance pipeline at a predetermined velocity to providereduced transportation costs. The flow of the slurry is interrupted at aconcentrating terminal and a portion of the water is removed therefromby conventional means such as partial filtration, centrifuging or-thermal treatment. The more concentrated slurry, that is, the slurryhaving a greater solids concentration than the slurry transportedthrough the long distance pipeline, is pumpable through a pipeline byconventional pumping means. The more concentrated slurry is also furtherstabilized in that it is statically stable and can be stored inconventional tank type storage means for extended periods of timewithout a substantial separation of the water from the coal particles.Moreover, the concentrated slurry is both statically and dynamicallystable in that there is little tendency for the coarser particles tosettle out more rapidly than the finer particles and there is littletendency for the heavy coarser particles to solidify or pack. The moreconcentrated slurry remains free flowing after substantial' periods ofstorage. The more concentrated slurry is withdrawn from the storagemeans at any desired rate and pumped through another pipeline either toor within the coal conversion terminal to a coal conversion unit. Thetransportation from the concentrating terminal to the conversionterminal is substantially simplified because the coal particles are nowhandled as a liquid instead of dry coal particles.

Another object of this invention is to provide a method of pumping acoal-Water slurry through a pipeline from a mine to a distant locationand thereafter increasing the solids concentration of the slurry andpumping theconcentrated slurry through another pipeline to a coalconversion unit.

A further object of this invention is to eliminate the necessity ofremoving substantially all of the water from the coal-water slurry.

A further object of this invention is to provide a method It is believedthat the iine coal particlesl of transporting coal to distant locationsthrough a pipeline and thereafter transporting the coal as aconcentrated slurry to a coal conversion unit.

These and other objects of this invention will be more completelydisclosed in the following specification, the accompanying drawings andthe appended claims.

In the drawings, FIGURE 1 is a schematic illustration of my improvedcoal pipeline transportation system.

`FIGURE. 2 is a schematic illustration of a coal pipeline system whereinthe slurry is transported to a concentrating terminal where the slurryis concentrated and thereafter transported through other pipelines to aplurality of coal conversion units.

Referring to the drawings wherein like numeral references designatesimilar parts in each gure, the numeral generally designates a slurrypreparation terminal which is located adjacent to a coal mining area ora coal cleaning plant. The coal is comminuted to a predetermined sizeconsist and is mixed with Water in slurry preparation apparatus 12.

The particulate coal has a spectrum of sizes that will provide minimumpumping costs when transported over long distances in the pipeline. Ithas been discovered when between about 2O to about 40 percent of thecoal particles are of a size that pass through a 325 mesh Tyler StandardScreen the tine coal particles serve with the water as a vehicle forother larger sized particles. For example, the larger sized particlesmay range in size from a top size of about 4 mesh Tyler Standard Screenand have a spectrum of smaller sizes. The coal particles, that is, boththe ne and coarse particles, are mixed with water to form a coal-waterslurry having a solids concentration of between 35 and 60 percent byweight coal particles. It has been discovered that a slurry prepared asdescribed above is dynamically stable in that the tendency of the largersized coal particles to settle out of the slurry is reduced and lessenergy is required to maintain the larger sized particles in suspensionwhile the slurry is transported through the pipeline. The dynamicallystable slurry provides optimum transportation costs over long distances.

The slurry is withdrawn from the slurry preparation apparatus 12 andtransported by means of pump 14 through a long distance pipeline 16. Theslurry is transported through the pipeline 16 at a velocity whichmaintains the coal particles uniformly suspended in the water. Forexample, the slurry may be transported through the pipeline atvelocities between 3 and 7 feet per second.

At intervals along the pipeline additional pumps 18 maintain the desiredvelocity of the slurry from the preparation terminal 10 to aconcentrating terminal generally designated by the numeral 20.

The concentrating terminal 20 in FIGURE l is indicated as being spacedfrom the coal conversion terminal 22. It should be understood, however,that the concentrating terminal 20 may form an integral part of the coalconversion terminal 22 where the entire output of the pipeline isconsumed at the coal conversion terminal and space for storage isavailable adjacent the conversion units. The concentrating terminal 20includes slurry treating apparatus 24 where a portion of the water isremoved from the slurry. Slurry treatment apparatus 24 is schematicallyillustrated and may include any suitable mechanical means for removing aportion of the water from the slurry. The slurry is concentrated in theslurry treating apparatus 24 to provide a more concentrated slurry thatis both statically and dynamically stable. The concentrated slurryshould have a solids concentration of between 60 and 75 percent coal byweight. The substantial amount of extremely ne coal particles in theslurry now makes it possible to increase the slurry concentration tobetween 60 and 75 percent solids and yet have a slurry that retains itsflow characteristics. The concentrated slurry is statically stable inthat there is no substantial segregation of coal particles according tosize while the concentrated slurry is stored under quiescent conditions.The larger sized particles remain substantially uniformly suspendedthroughout the concentrated slurry even after extended periods of timeunder quiescent conditions. There is little tendency of the heavycoarser particles to solidify or pack so that the concentrated slurryretains the desirable properties of a liquid. At this increasedconcentration the concentrated slurry is readily pumpable through apipeline with conventional pumping apparatus. The pumping costs, becauseof the increased solids concentration, are substantially greater thanthat of the more dilute dynamically stable slurry that is transportedover long distances through the long distance pipeline. These additionalpumping costs are offset many times by the advantages now present instoring and handling the coal particles as a highly concentrated slurry.

Referring again to FIGURE l, the concentrated slurry withdrawn fromslurry treating apparatus 24 is pumped by means of pump 26 to a slurrystorage tank 28 where the statically stable concentrated slurry may bestored for extended periods of time without substantial size segregationof the particles in the slurry. As stated above, the concentrated slurryis statically stable and the coal particles do not have a tendency topack or form an immobile mass of solids as is the case when a diluteslurry is permitted to stand under quiescent conditions for a shortperiod of time.

The concentrated slurry is withdrawn from the storage tank 28 and pumpedthrough another pipeline 30 by means of a pump 32 to the coal conversionterminal 22. A metering or control device 34 is positioned in thepipeline 30 to control the amount of coal that is introduced into theconversion apparatus. The concentrated slurry from pipeline 30 may taketwo alternative routes in the coal conversion terminal 22 as illustratedin FIGURE l. If the burner of furnace 36 is adapted to burn a slurryhaving a concentration of between 60 and 75 percent solids, theconcentrated slurry is pumped from pipeline 39 through a branch conduit38 directly into the burner apparatus 40. If the burner is one whichoperates at maximum efliciency when all the coal particles have a sizewhich passes through a 200 mesh Tyler Standard Screen, the concentratedslurry from pipe line 30 is introduced into a comminuting means 42.Heated gas is introduced into comminuting means 42 at a predeterminedvelocity through conduit 44. The heated gas vaporizes the water in theslurry and conveys as a suspension the coal particles, certain of whichare comminuted in comminuting means 42, through conduit 46 to the burner4G. Valve means are provided in pipeline 30 and conduit 38 to controlthe flow of concentrated slurry into burner 40. It will be noted in theabove description that there is a closed circuit from the slurrypreparation terminal 1i) to the place of coal conversion which in thisinstance is burner 40. Within the concentrating terminal 20 the slurryis concentrated and stored as a dynamically and statically stable slurryin the storage tank 28. The concentrated slurry is transported from theconcentrating terminal 2i) to the coal conversion terminal 22 by pumpingthe concentrated slurry through another pipeline. rl`he concentratedslurry is further transported through the coal conversion terminal 22 tothe coal conversion unit 36 by pumping the concentrated slurry throughother conduits or pipes. The method described eliminates the dusthazards and storage problems heretofore described and further provides ameans whereby coal particles can be accurately metered into the coalconversion unit In FIGURE 2 there is illustrated another arrangementwhereby the statically and dynamically stable concentrated slurry istransported from a concentrating terminal to a plurality of coalconversion units which may be located in a single coal conversionterminal or a plurality of coal conversion terminals spaced atsubstantial distances from each other. The arrangement schematicallyillustrated in FIGURE 2 provides a means whereby the output of the coalpipeline 16 may be distributed to a series of coal conversion units notnecessarily within the contines of a single coal conversion terminal.For example, the dynamically and statically stable concentrated slurrycan -be transported to a plurality of power plants located around theperiphery of a large metropolitan area, or the dynamically andstatically stable concentrated slurry may supply other conversion unitssuch as coke ovens, blast furnaces, or the like.

Referring to FIGURE 2 the coal conversion terminals are generallydesignated by the numerals 11i), 120, and 136 respectively. Each of thecoal conversion terminals includes a coal conversion unit generallydesignated by the numerals 112, 122, and 132 respectively. The otherapparatus illustrated in FIGURE 2 are similar to that of FIGURE 1 andhave the same numerals. In FIGURE 2 there is illustrated a means ofsupplying the plurality of coal conversion units 112, 122 and 132 inconversion terminals 110, 120 and 130 from the central concentrat ingterminal 20. The various valves 114, 124 and 134 in the respectivebranch conduits 138, 140 and 142 control the ytlow of concentratedslurry from the pipeline 30 to the respective coal conversion units 112,122 and 132.

1t will be appreciated from the brief description of FIGURE 2 that it isnow possible to supply coal from a distant mine to a coal conversioncomplex which includes a concentrating terminal and a plurality of coalconversion terminals. The coal may be conveniently stored within theconcentrating terminal as a dynamically and statically stable slurry.The concentrated slurry may be transported from the concentratingterminal to the respective coal conversion units at any desired rate.

The following are two examples of how my improved method may bepracticed.

A coal-water slurry is prepared in the slurry preparation terminal 1b. Arepresentative size consist and size distribution of the coal particlesis as follows:

Weight percent of coal (Tyler Standard Screen):

rThe coal particles are mixed with water to have a solids concentrationof about 55 percent coal by weight in water. The coal is transportedthrough the pipeline 16 at a velocity of between about 4 and 6 feet persecond to the concentrating terminal 20. The slurry is introduced intothe slurry treatment apparatus 24 where sutcient water is removed fromthe slurry to provide a concentrated slurry having a concentration ofabout 72 percent by weight of coal in water. The concentrated slurry ispumped by means of pump 26 to slurry storage vessel 2S and pumped fromstorage vessel 28 through pipeline Sii to a coal conversion unit.

Another example of how my invention may be practiced is as follows. Theslurry is prepared in the slurry preparation terminal by mixing coalparticles having the following representative size consist:

Weight percent of coal (Tyler Standard Screen):

Percent on 8 mesh 8.2

on 14 mesh 22.8 on 28 mesh 20.5

on 48 mesh 12 on l0() mesh 6.1

on 200 mesh 2.6 on 325 mesh 1.1

through 325 mesh 26.7

with water to form a slurry having between 50 and 6.0 percent by weightof coal in water, transporting the slurry through the pipeline 16 at apredetermined velocity to provide minimum pumping costs, introducing theslurry into slurry treatment apparatus 24 in the concentrating terminal20, removing a portion of the water from the slurry so that aconcentrated slurry having a concentration of between about 6G and 70percent coal by weight is obtained. The concentrated slurry istransported from slurry treatment apparatus 24 by means of pump 2e toslurry storage vessel 28 where the concentrated slurry may be maintainedfor extended periods of time under quiescent conditions. As required,slurry is withdrawn from slurry storage vessel 26 and pumped by means ofpump 32 through pipeline 30 to coal conversion terminal 22.

It should be understood that the size consist of the coal particles inthe slurry may deviate substantially from the representative sizeconsist set forth in the examples and the examples are for illustrativepurposes only. It has been discovered to obtain the desired dynamicstability during transportation through the long distance pipeline andto obtain a statically and dynamically stable concentrated slurry at theconcentrating terminal that the slurry should include between about 20and 40 percent of the coal particles with a size which passes through a325 mesh Tyler Standard Screen. When about 20 percent of the coalparticles are of a size which passes through a 325 mesh Tyler StandardScreen the coarser particles should have a top size not greater than 4mesh Tyler Standard Screen to obtain the desired dynamic stability. Whenthe content of the tine particles which pass through a 325 mesh TylerStandard Screen is increased above 20 percent, the coarse particle topsize may lalso be increased.

According to the provisions of the patent statutes, l have explained theprinciple, preferred construction and mode of operation of my inventionand have illustrated and described what I now consider to represent itsbest embodiments. However, I desire to have it understood, that withinthe scope of the appended claims the invention may be practicedotherwise than as Vspeciiicaily illustrated and described.

I claim:

1. A method of transporting coal over long distances for conversion atdistant locations which comprises preparing a slurry of coal and watercomprising between 35 and 60 percent by weight of Said coal in saidwater, said coal having a spectrum of sizes with a top size of about 4mesh Tyler Standard Screen, transporting said slurry through a pipelineover long distances to a distant location, interrupting thetransportation of said slurry at said distant location, thereafteradjusting the solids concentration of said slurry so that saidconcentrated slurry has between about 6() and 75 percent by weight ofsaid coal in said water, transporting said concentrated slurry through asecond pipeline over a shorter distance to a second location, andconverting said coal in said concentrated slurry at said secondlocation.

2. A methody of transporting coal over long distances for conversion atdistant locations which comprises obtaining coal having a spectrum ofsizes and between about 20 and 40 percent by weight of 325 meshparticles, preparing a water slurry comprising between 35 and 60 percentby Weight of said coal in water, pumping said slurry through a pipelineat a velocity of between about 3 and 7 feet per second over longdistances to a distant location, interrupting the transportation or"said slurry at said distant location, thereafter removing a portion ofsaid water from said slurry to provide a concentrated slurry having asolids concentration of between 60 and 75 percent by weight of said coalin said water, pumping said concentrated slurry through a secondpipeline over a shorter distance to a second location, and convertingthe coal in said concentrated slurry at said second location.

3. A method f transporting coal over long distances for conversion atdistant locations which comprises preparing a slurry of particulate coaland water, said particulate coal having a spectrum of sizes a portion ofwhich passes through a 325 mesh Tyler Standard Screen, 'said slurryhaving solids concentration and size distribution so that said solidparticles remain uniformly suspended in said water while beingtransported through a pipeline at a velocity of between about 3 and 7feet per second, pumping said slurry through a pipeline at a velocity ofbetween 3 and 7 feet per second over long distances to a distantlocation, interrupting the transportation of said slurry at said distantlocation, thereafter removing a portion of the water in said slurry toprovide a concentrated slurry having a solids concentraiton of between60 and 75 percent by weight of said coal in said water, pumping saidconcentrated slurry through a second pipeline to a second location andconverting the coal in said concentrated slurry at said second location.

4. A method of moving coal from a mine to a distant location forconversion thereat which comprises preparing a slurry of coal and waterwhich has a concentration of between 35 and 60 percent by weight of saidcoal, said coal in said slurry having a spectrum of sizes, pumping saidslurry through a pipeline at a velocity of between about 3 and 7 feetper second over long distances to a concentrating terminal, interruptingthe transportation of said slurry at said concentrating terminal,thereafter adjusting the solids concentration of said slurry in saidconcentrating terminal to provide a more concentrated slurry having asolids concentration of between 60 and 75 percent by weight of said coalin said water, pumping said concentrated slurry through a secondpipeline to a coal conversion terminal, and converting said coal in saidconcentrated slurry in coal conversion apparatus in said conversionterminal.

5. A method of transporting coal over long distances for conversion atdistant locations which comprises preparing a slurry of coal and waterhaving a concentration of between 35 and 60 percent by weight of saidcoal in said water, said coal having a spectrum of sizes and hetween 20and 40 percent of said coal having a size which will pass through a 325mesh Tyler Standard Screen, pumping said slurry through a pipeline overlong distances to a coal burning terminal, interrupting thetransportation of said slurry adjacent said coal burning terminal,removing a portion of said water in said slurry to provide a moreconcentrated slurry having a concentration between 60 and 75 percent byweight of said coal in said water, pumping said concentrated slurrythrough a second pipeline to said coal 4burning terminal and in saidcoal burning terminal to coal burning apparatus, and burning the coal insaid concentrated slurry in said coal burning apparatus.

6. A method of transporting coal over long distances for conversion atdistant locations which comprises preparing a slurry of coal and waterhaving a concentration of between and 60 percent by weight of said coalin water, said coal particles having a spectrum of sizes and between 20and 40 percent by weight of said coal particles having a size which willpass through a -325 mesh Tyler Standard Screen, pumping said slurrythrough a Apipeline at a velocity `of between 3 and 7 feet per secondover long distances to a conversion terminal, interrupting thetransportation of said slurry, thereafter adjusting the solidsconcentration of said slurry to provide a 'more concentrated slurryhaving a solids concentration Yof between and 75 percent solids byweight of said coal in water, said concentrated slurry being capable ofmaintaining said particles in suspension under quiescent conditions,maintaining an inventory of said concentrated slurry, pumping saidconcentrated slurry through a sec- -ond pipeline to coal conversionapparatus, metering said concentrated slurry at a controlled rate fromsaid pipe- ,line into said conversion apparatus for conversion of saidycoal therein.

7. A method of transporting coal over long distances `for conversion atdistant locations which comprises preparing a slurry of particulate coaland water having a concentration of between 35 and 60 percent by weightof said coal in water, said particulate coal having a spectrum of sizesand a substantial portion which is retained on a 200 mesh Tyler StandardScreen, said particulate coal having between 2O and 40 percent by weightwhich passes through a 325 mesh Tyler Standard Screen, pumping saidslurry through a pipeline at a velocity of between 3 and 7 feet persecond over a distance to a concentrating terminal, interrupting thetransportation of said slurry in said concentrating terminal, removing aportion of the water in said slurry to provide a concentrated slurryhaving a concentration of between 60 and 75 percent by weight of saidparticulate coal in said water, maintaining an inventory of saidconcentrated slurry 'within said concentrating terminal, pumping saidconcentrated slurry through a second pipeline to a coal burning terminaland in said coal burning terminal to coal pulverizing apparatus,supplying heated air to said coal pulverizing apparatus, vaporizing atleast a portion of said water in said concentrated slurry andcomminuting at least a portion of said coal particles having a sizewhich is retained on a 200 mesh Tyler Standard Screen to a size whichwill pass through a 200 mesh Tyler Standard Screen, conveying said coalparticles as a suspension in said vaporized water and said air to apulverized fuel burner and burning said coal particles in saidpulverized fuel burner.

No references cited.

1. A METHOD OF TRANSPORTING COAL OVER LONG DISTANCES FOR CONVERSION ATDISTANT LOCATIONS WHICH COMPRISES PREPARING A SLURRY OF COAL AND WATERCOMPRISING BETWEEN 35 AND 60 PERCENT BY WEIGHT OF SAOD COAL IN SAIDWATER, SAID COAL HAVING A SPECTRUM OF SIZES WITH A TOP SIZE OF ABOUT 4MESH TYLER STANDARD SCREEN, TRANSPORTING SAID SLURRY THROUGH A PIPELINEOVER LONG DISTANCES TO A DISTANT LOCATION, INTERRUPTING THETRANSPORTATION OF SAID SLURRY AT SAID DISTANT LOCATION, THEREAFTERADJUSTING THE SOLIDS CONCENTRATION OF SAID SLURRY SO THAT SAIDCONCENTRATED SLURRY HAS BETWEEN ABOUT 60 AND 75 PERCENT BY WEIGHT OFSAID COAL IN SAID WATER, TRANSPORTING SAID CONCENTRATED SLURRY THROUGH ASECOND PIPELINE OVER A SHORTER DISTANCE TO A SECOND LOCATION, ANDCONVERTING SAID COAL IN SAID CONCENTRATED SLURRY AT SAID SECONDLOCATION.